Platinum (Pt) is a dense, malleable, and silver-white transition metal with the atomic number 78. It is classified as a noble metal, a designation that speaks to its remarkable chemical stability and low reactivity. This rarity and resistance to chemical attack make it one of the most valuable precious metals on Earth, with a concentration in the Earth’s crust of only about 0.005 parts per million. Its inherent properties, including a high melting point of 1,768 degrees Celsius and exceptional resistance to corrosion, are the foundation for its applications in high-tech and medical fields.
The metal’s density (21.45 grams per cubic centimeter) and mechanical durability allow it to function reliably in environments where other metals would quickly degrade or fail. Platinum’s unique combination of physical and chemical traits has positioned it as an indispensable material in advanced scientific and health technologies.
Platinum in Cancer Therapy
Platinum-based compounds are used to treat nearly half of all people receiving chemotherapy for cancer. The most common agents are Cisplatin, Carboplatin, and Oxaliplatin, which leverage platinum’s chemical properties to interfere with the fundamental processes of cancer cells. These drugs are typically administered as coordination complexes of platinum, which are designed to become chemically active inside the cell.
The mechanism of action relies on the platinum complex binding directly to DNA, the cell’s genetic material. Specifically, the platinum atom reacts most commonly with the N-7 position of the guanine base on the DNA strand. This binding forms various types of crosslinks, particularly intrastrand crosslinks, which kink and distort the DNA’s helical structure.
The resulting DNA damage prevents the cell from accurately replicating its genetic material or undergoing transcription. This irreparable damage triggers the cell’s self-destruct mechanism, known as apoptosis, in the rapidly dividing cancerous cells. Cisplatin, the first of these drugs, has dramatically improved the cure rate for cancers such as testicular cancer. Researchers continue to develop new platinum-containing compounds to overcome drug resistance and reduce the associated side effects, such as neurotoxicity.
Essential Role in Chemical Catalysis
Platinum serves as a highly efficient catalyst, accelerating chemical reactions without being consumed. This property makes it valuable in industrial and environmental chemistry, where it is used to facilitate numerous reactions. For example, in automotive catalytic converters, platinum works to reduce harmful vehicle emissions.
In this application, platinum nanoparticles provide a surface where pollutants like carbon monoxide (CO) and unburnt hydrocarbons can bind. Platinum facilitates the oxidation of CO to less harmful carbon dioxide (CO2) and the conversion of hydrocarbons into CO2 and water vapor. Its high thermal durability and resistance to chemical poisoning make it particularly effective, especially in diesel applications where excess oxygen is present.
Platinum’s catalytic activity is also important in hydrogen fuel cells. Nanoparticles coat the anode and cathode, where they lower the activation energy required for the electrochemical reactions. At the anode, platinum enables the oxidation of hydrogen into protons and electrons. At the cathode, it facilitates the reaction of these protons and electrons with oxygen to form water. This efficient process generates electricity with water as the only byproduct, making platinum a central component in clean energy technology.
Scientific Measurement and Sensing
The stable electrical and thermal properties of platinum make it an ideal material for high-precision scientific instrumentation. One of its most common uses is in Resistance Temperature Detectors (RTDs), also known as platinum resistance thermometers (PRTs). RTDs operate on the principle that the electrical resistance of platinum changes predictably and repeatably with temperature.
Platinum’s stability ensures that this temperature-resistance relationship remains constant over a long period, providing highly accurate and repeatable measurements. These sensors are used across a wide temperature range, often from -200 degrees Celsius to over 600 degrees Celsius, and are employed for industrial process control and laboratory analysis. Platinum RTDs have been adopted as the international standard for temperature interpolation by institutions like the National Institute of Standards and Technology.
Platinum is also used as an inert electrode material in electrochemical applications, such as in pH meters and other laboratory cells. Its resistance to corrosion and chemical attack ensures that the electrode does not react with the sample being analyzed, which is essential for accurate measurement. This chemical inertness, combined with its excellent electrical conductivity, allows platinum electrodes to reliably transmit electrical signals for precise analytical work.
Medical Implants and Biocompatibility
Platinum’s exceptional biocompatibility means it can exist within the human body without causing adverse reactions or corrosion, making it suitable for long-term medical devices. Its chemical inertness prevents the metal from degrading in the body’s saline environment and from causing toxic or allergic responses. This property is distinct from the chemically active role of platinum in chemotherapy drugs.
The metal is used extensively as an inert component in devices that require long-term reliability and precise electrical function. For instance, platinum and its alloys are used for the wiring and electrodes in pacemakers and implantable defibrillators. Platinum’s excellent electrical conductivity ensures the efficient transmission of the impulses needed to regulate heartbeats, while its resistance to corrosion guarantees the device’s durability.
Furthermore, platinum is a component in cochlear implants, neurostimulators, and certain types of stents used in treating coronary artery disease. Its radiopacity, the ability to block X-rays, makes it visible under imaging, which is a practical benefit for surgeons placing stents or other implantable devices. The metal can be manufactured into fine wires, sheets, and micro-machined parts due to its malleability, allowing for the miniaturization required in modern implant technology.